Step 7 · Tighten Locknut and Clean Excess Putty
While holding the strainer from above to prevent it from spinning (using pliers in the basket or a helper), use your channel-lock pliers or strainer wrench to tighten the locknut from below. Tighten it firmly to compress the rubber gasket and squeeze out the excess plumber's putty above the sink. A good rule of thumb is to give it a quarter-turn past hand-tight. Do not overtighten. Once tight, go above the sink and use your finger or a cloth to wipe away the excess putty that has squeezed out. Use the plastic putty knife for any stubborn bits.